سنن النسائي

It was narrated that Ubayy bin Ka'b said: "The Messenger of Allah (ﷺ) taught me a surah, and when I was sitting in the masjid I heard a man reciting it in a way that was different from mine. I said to him: 'Who taught you this surah?' He said: 'The Messenger of Allah (ﷺ).' I said: 'Stay with me until we go to the Messenger of Allah (ﷺ).' So we came to him and I said: 'O Messenger of Allah, this man recites a surah that you taught me differently.' The Messenger of Allah (ﷺ) said: 'Recite, O Ubayy.' So I recited it, and the Messenger of Allah (ﷺ) said to me: 'You have done well.' Then he said to the man: 'Recite.' So he recited it and it was different to my recitation. The Messenger of Allah (ﷺ) said to him: 'You have done well.' Then the Messenger of Allah (ﷺ) said: 'O Ubayy, the Quran has been revealed with seven different modes of reciation, all of which are good and sound."